Technical Abstract:
As of 2010, there were 57,000 acres of commercially-grown pears in the United States with a total crop value of $382 million. The industry has been stagnating due to a declining consumption of processed pears and competition from imported pears and other fruits, as reflected in the loss of 10,000 acres or 15 percent since 2000. Two major factors in pear acreage decline are the lack of precocity and high cost of production. Existing mature trees are large and widely spaced in orchards, and new trees are slow to bear, which discourages replanting. Close spacing accelerates per acre yields, but trees that are planted more closely tend to overgrow their space because growers must still rely on standard rootstocks. Pears are also extremely labor intensive. The U.S. pear orchard situation is in contrast to European, and to a lesser extent, South American orchards, which successfully utilize the truly dwarfing rootstock quince (Cydonia oblonga L.), which has enabled high density plantings and modern training systems. Quince has thus far been found to lack desirable horticultural characteristics, e.g., cold hardiness in the Pacific Northwest, long-term vigor and productivity in California, and fire blight tolerance. Because of the above described scenario, there is a broad and deep consensus among all sectors of the U.S. pear industry that achieving efficient (precocious, good yield, fruit size), truly size-controlling rootstocks is imperative for the pear industry to remain competitive nationally and globally. Most U.S. effort has focused on evaluating commercially available rootstocks from the U.S. or other countries, and advanced selections from international sources. Worldwide, there are at least 12 active breeding programs developing Pyrus rootstocks for European pear and at least nine additional developing quince rootstocks for pear. A review of the literature identified 24 evaluation programs. This presentation will summarize the current breeding and evaluation research, as well as orchard systems trails in the US. We will also outline needed basic and applied research, based on experience, and stakeholder input from both the Pacific Northwest and California have defined a number of basic and applied research and extension needs: a detailed analysis of the effects of dwarfing rootstocks on scion, the underlying mechanisms of dwarfing in pear (i.e. graft incompatibility, water relations, nutrient uptake and synthesis, photosynthate and carbohydrate synthesis and distribution, phytohormone metabolism and transport, the inheritance of key traits, and selection criteria for breeding). Applied research needs include efficient propagation and orchard systems.